1. Field of the Invention
This invention relates to articles made by lithographic processes and in particular to processes made utilizing a lithographic material that requires wet development.
2. Art of the Invention
A variety of articles such as lithographic masks or integrated circuits are manufactured by a series of steps including a lithographic processing step. In such lithographic processing stops a radiation sensitive material generally denominated a resist is exposed to actinic radiation in a desired pattern. The radiation in a positive resist induces a chemical reaction in the impacted area and produces a higher solubility in exposed regions relative to unexposed regions. During development, this differential solubility is then utilized to remove the exposed regions by immersion in or spraying with a suitable solvent.
The development of the exposed resist material must be performed under conditions that ensures that the regions to be removed are indeed essentially totally removed. Thus, generally an overdevelopment is performed. This overdevelopment i.e., development for a time longer than that required to totally clear at least a portion of the exposed region, ensures that all regions to be removed are cleared. (Features in different geometric surrounding generally develop at different rates and thus necessitate such overdevelopment.) The rate of development is strongly dependent for many resists such as poly 1-butene sulfone (PBS) on environmental conditions such as relative humidity as well as on the actual processing conditions. Therefore, generally resist development is performed in a controlled environment to improve reproducibility. Such controlled environments typically involve a controlled environmental chamber surrounding the development apparatus that in turn requires a large capital investment, as well as associated maintenance and operating costs.
Despite the presence of a controlled environment, resists are generally not developed for a pre-established period of time. Typically, development is performed, the resist material is inspected to see if all exposed dimensions have reached their desired size, and the development and inspection procedure is iterated until this size is reached. This labor-intensive processing together with the previously discussed capital investment and costs is obviously not entirely desirable. Additionally, the necessitated increased handling tends to introduce contamination into the process thereby increasing lithographic defects with a concomitant decrease in product yield.
Therefore, any procedure including a lithographic processing step for producing an article would significantly benefit from the successful elimination of a controlled environment and substantial operator handling e.g., iterative processing.